Virtual machine file-level restoration

ABSTRACT

Disclosed is a method and system for selectively restoring file-level data from a disk image backup. In embodiments, a virtual machine backup may be performed by dividing a virtual machine virtual disk file into a plurality of discrete fixed-sized data blocks sharing a common index file that is stored on a backup medium, such as a hard drive, to form a backup set. The index file is referenced to determine which fixed-sized block contains volume information, such as a partition table, of the backed-up virtual machine file. The individual blocks are processed as a virtual filesystem which is mounted and presented to an access module, which traverses the filesystem and provide access to individual files in the image backup to a client process. The restore files may be delivered to the client in a container file, which may be compressed to increase transfer speed. The container file may include executable instructions for automatically restoring the files to a desired location.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S.Provisional Application Ser. No. 61/168,315, filed on Apr. 10, 2009,entitled “VIRTUAL MACHINE DATA BACKUP”; U.S. Provisional ApplicationSer. No. 61/168,318, filed on Apr. 10, 2009, entitled “VIRTUAL MACHINEFILE-LEVEL RESTORATION”; and U.S. Provisional Application Ser. No.61/172,435, filed on Apr. 24, 2009, entitled “VIRTUAL MACHINE DATAREPLICATION”; the entirety of each are hereby incorporated by referenceherein for all purposes.

BACKGROUND

1. Technical Field

The present disclosure relates to computer data backup, and inparticular, to a system and method for performing block-level backups ofvirtual machine, wherein backed up data is stored in de-duplicated formin a hierarchical directory structure.

2. Background of Related Art

Continuing advances in storage technology allow vast amounts of digitaldata to be stored cheaply and efficiently. However, in the event of afailure or catastrophe, equally vast amounts of data can be lost.Therefore, data backup is a critical component of computer-basedsystems. As used herein, the term “backup” may refer to the act ofcreating copies of data, and may refer to the actual backed-up copy ofthe original data. The original data typically resides on a hard drive,or on an array of hard drives, but may also reside on other forms ofstorage media, such as solid state memory. Data backups are necessaryfor several reasons, including disaster recovery, restoring data lostdue to storage media failure, recovering accidentally deleted data, andrepairing corrupted data resulting from malfunctioning or malicioussoftware.

A virtual machine (VM) is a software abstraction of an underlyingphysical (i.e., hardware) machine which enables one or more instances ofan operating system, or even one or more operating systems, to runconcurrently on a physical host machine. Virtual machines have becomepopular with administrators of data centers, which can contain dozens,hundreds, or even thousands of physical machines. The use of virtualservers greatly simplifies the task of configuring and administeringservers in a large scale environment, because a virtual machine may bequickly placed into service without incurring the expense ofprovisioning a hardware machine at a data center. Virtualization ishighly scalable, enabling servers to be allocated or deallocated inresponse to changes in demand. Support and administration requirementsmay be reduced because virtual servers are readily monitored andaccessed using remote administration tools and diagnostic software.

In one aspect, a virtual server consists of three components. The firstcomponent is virtualization software configured to run on the hostmachine which performs the hardware abstraction, often referred to as ahypervisor. The second component is a data file which represents thefilesystem of the virtual machine, which typically contains the virtualmachine's operating system, applications, data files, etc. A virtualmachine data file may be a hard disk image file, such as, withoutlimitation, a Virtual Machine Disk Format (VMDK) format file. Thus, foreach virtual machine, a separate virtual machine file is required. Thethird component is the physical machine on which the virtualizationsoftware executes. A physical machine may include a processor,random-access memory, internal or external disk storage, andinput/output interfaces, such as network, storage, and desktopinterfaces (e.g., keyboard, pointing device, and graphic displayinterfaces.)

Virtual machine files may be backed up as images, or replications of thecomplete virtual machine file. Such backup schemes may logically divideand store the virtual machine file into a number of smaller logicalblocks which, taken together, constitute a “snapshot” of an entirefilesystem as it existed at the time the backup was performed. Whilesuch systems are well-suited for restoring an entire filesystem, suchsystems may have drawbacks, for example, if it is desired to restore asubset of the filesystem, such as an individual file, or a singledirectory, or an arbitrary collection of files and/or directories, fromthe backup. A backup system which performs virtual server backups withincreased efficiency and effectiveness while permitting the restorationof individual files, folders, and backup subsets would be a welcomeadvance.

SUMMARY

The present disclosure is directed to a method of performing file levelrestoration of a volume level backup set, or archive. In one embodiment,the backup set includes a plurality of fixed-sized blocks representativeof a virtual machine file (e.g., a virtual disk file and/or a VMDK file)and an index file indicative, at least in part, of the positions of theindividual fixed-size blocks within the archive. Such a backup isdescribed in the commonly-owned, concurrently-filed U.S. patentapplication Ser. No. 12/758,245 entitled “VIRTUAL MACHINE DATA BACKUP”,the entirety of which is hereby incorporated by reference herein for allpurposes. The index file is consulted to determine which fixed-sizeddatablock(s) include filesystem information, e.g., a file allocationtable (FAT), a master file table (MFT), and the like, of the backed-upvirtual machine file. An offset, or pointer, into the fixed-sizeddatablock(s) may be established to define a position within thefixed-sized datablock(s) at which the filesystem information resides.

The disclosed method processes 1 MB fixed-length blocks of data of avirtual machine file. A MD5 hash is created for this block data. The 1MB of data can be compressed, or left uncompressed. The 1 MB of data isstored as a single file. The file name is the MD5 hash value of the 1 MBdata block. The hash of this file is saved to a separate index file forlater use to retrieve, validate, and rebuild the backup data. The datablocks, whether in compressed or uncompressed form, are stored at astorage destination, in a unique directory structure consisting of 256first level directories designated as 00-FF, each having 256 secondlevel directories designated as 00-FF within, comprising 65,536directories in total. The 1 MB compressed (or uncompressed) data filesare stored in the directory structure based on the first four bytes ofthe hash, e.g.,

-   -   “./00/22/T.002249a8a218ef8a4da87550f388942d.gz”.

The first four bytes of data for the file name are “0022”. The file isstored in directory “./00/22/”. The .gz extension indicates the file iscompressed.

Subsequent backups are performed having as a destination the samestorage location. Data blocks are generated using the above unique hash.A file query is made to the storage location to see if there is alreadya file existing with the same hash. If the file does not exist, thesource data is written into the directory hierarchy with the hash as thefile name and an index file is updated. If the file exists, then onlythe index file is updated for the current backup being run.

Over time the directory structure will accumulate data blocks from allbackups sent thereto. A separate index file is created for each backup,and is used to keep track of the blocks of data for, e.g., re-assemblingdata block of the original source during restoration.

The use of a hash also provides a self-checking mechanism which enablesself-validation of the data within the stored file. A routine isscheduled to run on an ad-hoc or periodic basis that reads the datawithin a stored file, and validates the data in the file to verify amatch to the hash file name. If the data does not match, the block isconsidered suspect, and is slated to be deleted. All associated backupsthat include this data block are flagged as “bad”. The index filecorresponding to backups so flagged may additionally or alternativelyinclude a “bad” flag.

In an embodiment, the data blocks (e.g., the 1 MB data blocks) may beevaluated to determine whether the data contained therein exhibits apredefined (“special”) data pattern. For example with limitation, aspecial data pattern may include a particular or repeating pattern,e.g., a data block consisting entirely of zero (00H) bytes. In thisinstance, a special hash is generated that represents the special datablock containing the particular data pattern. The special hash may behard-coded, defined in a database, and/or defined in a configurationfile. Since the contents of a special data block is predefined, it isonly necessary to record the fact that the data block is special. It isunnecessary to store the actual contents of a special block. Thus, foreach data block identified as special, the index file is updatedaccordingly and the backup proceeds. In this manner, resources areconserved since special blocks, e.g., null blocks, do not consume spaceon the storage device, do not use communication bandwidth during backupand restoration procedures, do not require as much computationalresources, and so forth. This provides a quick and easy way to skipspecial (e.g., null) data in a given backup set.

During restoration, the fixed-sized datablock(s) are piped through avirtual filesystem component, such as without limitation, a Filesystemin Userspace (FUSE) driver. The virtual filesystem driver presents thefilesystem of the backup set to an access module, which may traverse thefilesystem and provide access to the backed-up files to a clientprocess. It is envisioned that a client process may include a web (e.g.,HTTP-based) interface, however, other client processes are contemplatedwithin the scope of the present disclosure, including without limitationan automated agent, a command line (shell) process, a remote procedurecall (RPC), a remote mounting client (NFS, SMB), and a database.

In embodiments, the access module may provide access to a plurality ofavailable backup sets. For example, multiple backup sets of a particularvirtual machine, taken at successive points in time, may be accessed bythe access module. Access to backup sets of multiple virtual machines,clustered machines, and the like are also contemplated within the scopeof the present disclosure. The disclosed method may sequentially,randomly, or concurrently process data blocks to service more than oneclient request at a time.

A user interface in accordance with the present disclosure may includelinks to backup sets, directories, files, and other logical groupings ofrestorable data. In an embodiment, the user interface is web-based(e.g., employs a web browser capable of communicating using thehypertext transfer protocol, a.k.a. HTTP, and the like.) Activation of alink may present hierarchical information, e.g., clicking on a backuplink may reveal the contents of the subject backup; clicking on adirectory (folder) link may present the contents thereof, and clickingon a file link may initiate a file transfer of the subject file to theclient machine. Additionally or alternatively, clicking on a folder mayinitiate a file transfer of the contents of the folder to the clientmachine. Other forms of delivery are contemplated, for example, multipleselections of backup data.

In an embodiment, the file transfer may include an aggregation stepwherein the file(s) are aggregated in a single container file fortransfer, e.g., requested files may be included in a .ZIP file forefficient and convenient transfer to the client. Also envisioned is acontainer file that includes executable instructions for automaticallymoving files to their original location within the target filesystem.

In yet another aspect, a method of data restoration in accordance withpresent disclosure includes retrieving a logical data unit stored withina backup set represented by at least one backup data block, and an indexfile. The disclosed method includes the steps of identifying a backupdata block containing information indicative of the logical organizationof the backup set. At least one logical data unit stored within thebackup set is identified. At least one identified logical data unit isselected, and the selected logical data unit is transferred to arecipient.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 shows a block diagram of an embodiment of a virtual machinebackup system in accordance with the present disclosure;

FIG. 2 is a block diagram illustrating a directory hierarchy of anembodiment of a virtual machine backup in accordance with the presentdisclosure; and

FIG. 3 is a flow diagram of an embodiment of a virtual machine backup inaccordance with the present disclosure;

FIG. 4 is a flowchart of an embodiment of a virtual machine backupmethod in accordance with the present disclosure; and

FIG. 5 illustrates a block diagram of a virtual machine backup system inaccordance with the present disclosure.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings; however, it isto be understood that the disclosed embodiments are merely examples ofthe disclosure, which may be embodied in various forms. Well-knownfunctions or constructions are not described in detail to avoidobscuring the present disclosure in unnecessary detail. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representative basis for teaching one skilled in the art to variouslyemploy the present disclosure in virtually any appropriately detailedstructure. In the discussion contained herein, the terms user interfaceelement and/or button are understood to be non-limiting, and includeother user interface elements such as, without limitation, a hyperlink,clickable image, and the like.

Additionally, the present invention may be described herein in terms offunctional block components, code listings, optional selections, pagedisplays, and various processing steps. It should be appreciated thatsuch functional blocks may be realized by any number of hardware and/orsoftware components configured to perform the specified functions. Forexample, the present invention may employ various integrated circuitcomponents, e.g., memory elements, processing elements, logic elements,look-up tables, and the like, which may carry out a variety of functionsunder the control of one or more microprocessors or other controldevices.

Similarly, the software elements of the present invention may beimplemented with any programming or scripting language such as C, C++,C#, Java, COBOL, assembler, PERL, Python, PHP, or the like, with thevarious algorithms being implemented with any combination of datastructures, objects, processes, routines or other programming elements.The object code created may be executed by any computer having anInternet Web Browser, on a variety of operating systems includingWindows, Macintosh, and/or Linux.

Further, it should be noted that the present invention may employ anynumber of conventional techniques for data transmission, signaling, dataprocessing, network control, and the like.

It should be appreciated that the particular implementations shown anddescribed herein are illustrative of the invention and its best mode andare not intended to otherwise limit the scope of the present inventionin any way. Examples are presented herein which may include sample dataitems (e.g., names, dates, etc.) which are intended as examples and arenot to be construed as limiting. Indeed, for the sake of brevity,conventional data networking, application development and otherfunctional aspects of the systems (and components of the individualoperating components of the systems) may not be described in detailherein. Furthermore, the connecting lines shown in the various figurescontained herein are intended to represent example functionalrelationships and/or physical or virtual couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical or virtual connections may bepresent in a practical electronic data communications system.

As will be appreciated by one of ordinary skill in the art, the presentinvention may be embodied as a method, a data processing system, adevice for data processing, and/or a computer program product.Accordingly, the present invention may take the form of an entirelysoftware embodiment, an entirely hardware embodiment, or an embodimentcombining aspects of both software and hardware. Furthermore, thepresent invention may take the form of a computer program product on acomputer-readable storage medium having computer-readable program codemeans embodied in the storage medium. Any suitable computer-readablestorage medium may be utilized, including hard disks, CD-ROM, DVD-ROM,optical storage devices, magnetic storage devices, semiconductor storagedevices (e.g., USB thumb drives) and/or the like.

The present invention is described below with reference to blockdiagrams and flowchart illustrations of methods, apparatus (e.g.,systems), and computer program products according to various aspects ofthe invention. It will be understood that each functional block of theblock diagrams and the flowchart illustrations, and combinations offunctional blocks in the block diagrams and flowchart illustrations,respectively, can be implemented by computer program instructions. Thesecomputer program instructions may be loaded onto a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructionsthat execute on the computer or other programmable data processingapparatus create means for implementing the functions specified in theflowchart block or blocks.

These computer program instructions may also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meansthat implement the function specified in the flowchart block or blocks.The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer-implemented process such that theinstructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

Accordingly, functional blocks of the block diagrams and flowchartillustrations support combinations of means for performing the specifiedfunctions, combinations of steps for performing the specified functions,and program instruction means for performing the specified functions. Itwill also be understood that each functional block of the block diagramsand flowchart illustrations, and combinations of functional blocks inthe block diagrams and flowchart illustrations, can be implemented byeither special purpose hardware-based computer systems that perform thespecified functions or steps, or suitable combinations of specialpurpose hardware and computer instructions.

One skilled in the art will also appreciate that, for security reasons,any databases, systems, or components of the present invention mayconsist of any combination of databases or components at a singlelocation or at multiple locations, wherein each database or systemincludes any of various suitable security features, such as firewalls,access codes, encryption, de-encryption, compression, decompression,and/or the like.

The scope of the invention should be determined by the appended claimsand their legal equivalents, rather than by the examples given herein.For example, the steps recited in any method claims may be executed inany order and are not limited to the order presented in the claims.Moreover, no element is essential to the practice of the inventionunless specifically described herein as “critical” or “essential.”

FIG. 1 illustrates a representative operating environment 100 for anexample embodiment of a virtual machine backup system 105 having thecapability to perform a file-level restoration in accordance with thepresent disclosure. Representative operating environment 100 includesvirtual machine backup system 105 which can be a personal computer (PC)or a server, which further includes at least one system bus 150 whichcouples system components, including at least one processor 110; asystem memory 115 which may include random-access memory (RAM); at leastone storage device 130, such as without limitation one or more harddisks, CD-ROMs or DVD-ROMs, or other non-volatile storage devices, suchas without limitation flash memory devices; and a data network interface140. System bus 150 may include any type of data communicationstructure, including without limitation a memory bus or memorycontroller, a peripheral bus, a virtual bus, a software bus, and/or alocal bus using any bus architecture such as without limitation PCI, USBor IEEE 1394 (Firewire). Data network interface 140 may be a wirednetwork interface such as a 100Base-T Fast Ethernet interface, or awireless network interface such as without limitation a wireless networkinterface compliant with the IEEE 802.11 (i.e., WiFi), GSM, or CDMAstandard.

Virtual machine backup system 105 may be operated in a networkedenvironment via data network interface 140, wherein system 105 isconnected to one or more virtual machine hosts 160 by a data network180, such as a local area network or the Internet, for the transmissionand reception of data, such as without limitation backing up andrestoring virtual machine data files as will be further describedherein. Each of the one or more virtual machine hosts 160 may includeone or more virtual machines 170 operating therein, as will beappreciated by the skilled artisan.

Virtual machine backup system 105 includes a virtual machine file-levelaccess module 120 that is configured to perform a method of filerestoration as described herein. The access module 120 includes avirtual filesystem driver module 125 having the capability to logicallyaccess a set of datablocks, such as without limitation a backup set, viathe native filesystem of source virtual machine from which the backupset is derived. In an embodiment, virtual filesystem driver module 125includes a filesystem in userspace (FUSE) software component. In anembodiment, access module 120 includes a set of programmableinstructions adapted to execute on processor 100 for performing themethod of virtual machine file-level restoration disclosed herein.

The present disclosure provides a method for restoring files from avirtual machine image backup. The virtual machine image backup mayinclude a plurality of fixed-size data blocks representative ofcorresponding blocks of the source virtual machine file, and an indexfile that may include, without limitation, a list of data blocks, aunique identifier (e.g., a hash value) that uniquely identify a datablock, date and time of backup, and source and destination locations.

Referring to FIGS. 2 and 3, a virtual machine file 420 slated for backupmay be stored on a storage device, such as without limitation, hard disk410. While it is contemplated that hard disk 410 may be included withina virtual machine host, is it to be understood that a virtual machinefile 420 may be stored on a hard disk array, such as a storage-areanetwork (SAN), a redundant array of independent disks (RAID),network-attached storage (NAS) and/or on any storage medium now or inthe future known.

The virtual machine file 420 is logically divided into a number offixed-length blocks 430 of like size. In one embodiment, a blocksize of1 MB is used, however, it is to be understood that a blocksize of lessthan 1 MB, or greater than 1 MB, may be used within the scope of thedisclosed method. In one aspect, the blocksize is determined at least inpart by a correlation between performance and blocksize. Otherparameters affecting blocksize may include, without limitation, a databus speed, a data bus width, a virtual machine file size, a processorspeed, a storage device bandwidth, and a network throughput. If avirtual machine does not precisely equal a multiple of a chosen fixedblocksize, the remainder may be padded with e.g., zeros, nulls, or anyother fill pattern, to achieve a set of equal-sized blocks.

An individual backup data file 445 is created from each fixed-lengthblock 430 of the virtual machine file 420. In an embodiment, individualbackup data file 445 may be given a temporary filename, and/or stored ina temporary location, e.g., /var/tmp/block000001.dat. A hash isgenerated according to the contents of each individual backup data file.In an embodiment, a 4,096 bit MD5 hash is used to create the hash valuefrom the contents thereof. The resultant hash value is stored in anindex file corresponding to the current backup session which store forlater use during, e.g., data restoration. The index file may include,without limitation, a list of data blocks comprising the backup set,hash values corresponding thereto, a date and time of backup, a sourcelocation, and a destination location. A collection of hash valuesrepresentative of a backup of virtual machine file, and data associatedtherewith, may be stored in an index file 455. Such a collection,together with the individual backup data files comprising the backed-upvirtual machine file 420 is known as a “backup set.”

Additionally or alternatively, the data block 430 may be compressedduring a compression step 432 using any suitable manner of datacompression, including without limitation, LZW, zip, gzip, rar, and/orbzip. Preferably, lossless data compression is used however in certainembodiments lossy data compression may advantageously be used.

The hash value may be regarded as a unique block identifier, or a uniqueidentifier of a backup data file 455. A non-temporary (“archival”)filename of the backup data file may be generated, at least in part,from the hash value, as illustrated in step 434. For example, thefilename of a backup data file 455 may be created by appending ahexadecimal representation of the hash value to a file prefix and/or toan appropriate file extension. Each backup data file 455 comprising thevirtual machine file therefore has a unique filename based upon the hashvalue.

A hierarchical directory structure 300 is provided on a backup storagedevice, e.g., storage device 130, for storing the backup data files. Thedisclosed structure has at a first level thereof a plurality ofdirectories 320 et seq. (e.g., folders). Each first level directorycontains therein a plurality of second level directories 330. In anembodiment, the hierarchy includes 256 first level directories, whereineach first level directory includes 256 second level directories, for atotal number of 65,536 directories. The first level and second leveldirectories may be named in accordance with a sixteen bit hexadecimalvalue, e.g., 00-FF. Thus, for example, a plurality of first leveldirectories may be named in accordance with the series ./00, ./01, 102 .. . ./FF while a second level of directories may be named ./00/01,./00/02/ . . . ./00/FF. Other directory mapping schemes are envisionedwithin the scope of the present disclosure, such as without limitation,a directory hierarchy having fewer than two levels, a directoryhierarchy having greater than two levels, a directory hierarchy having adirectory naming convention that includes fewer than a sixteen bithexadecimal value, a directory hierarchy having a directory namingconvention that includes greater than a sixteen bit hexadecimal value,and/or a directory hierarchy having a directory naming convention thatincludes an alternative naming encoding, such as octal, ASCII85, and thelike.

With reference to FIGS. 4 and 5, the disclosed method of performing afile-level restoration 200 starts with the step 205, which may includeinitialization, housekeeping, resource allocation (e.g., memoryallocation, opening I/O channels), and the like. In the step 210, adesired backup set is selected from one or more previously-createdbackup sets. In one non-limiting example, a user may choose a desiredbackup set based upon selection criteria such as date and time of backup(e.g., a timestamp), a source virtual machine (e.g., the machine fromwhich the backup was created), a file contained therein, contents of afile contained therein, and the like. In step 215, a set of data blocks445 which comprise a selected backup set are identified. In anembodiment, an index file 455 may be consulted to perform theidentification of data blocks stored within a directory hierarchy 300that comprise a desired backup set. At least one datablock 445 thatincludes, for example, volume information, such as a partition table,file allocation table, a master boot record, and the like, may beidentified in step 215. In the step 220 the identified datablocks aremounted as a virtual filesystem, using, for example, a Filesystem inUserspace (FUSE) driver 510 or the like. The virtual filesystem driver510 processes volume information contained within the data block, and/orprocesses block identification information stored within the index file,to obtain information relating to the content of the backup set. Inparticular, available logical units of data, such as directories andfiles that are contained within the backed-up filesystem are identified.In the step 225, the available files are presented to a client, whichmay be e.g., a user via a user interface and/or a client process via anapplication programming interface (API). At least one backed-up filecontained within the backup set is selected by the client process forrestoration. Advantageously, the virtual filesystem driver 510 enablesthe client (user) to browse the filesystem of the backup set tofacilitate the selection of backed-up filed for restoration. In the step230, the virtual filesystem driver reads the backup data blockscorresponding to the selected file(s) to reconstruct the selectedfile(s) for restoration. By way of non-limiting example only, thereconstructed files are represented by “file1.dat” 520, “file2.exe” 530,and/or “file3.txt” 540. The reconstructed file(s) for restoration aredelivered to the client in the step 240.

Optionally or alternatively, in the step 235 the reconstructed files“file1.dat” 520, “file2.exe” 530, and “file3.txt.” 540 etc. may beaggregated (e.g., combined into a container file) and/or compressed(e.g., into a .zip file.) In an envisioned embodiment, a container filemay be a self-restoring file 550 that includes a set of executableinstructions configured to perform at least one of decompressing thefiles contained within the container file, and copying the filescontained within the container file to a predetermined destination. Theself-restoring file may provide a user interface configured to accept atleast one user input indicative of a destination location, and to causethe self-restoring file to perform the indicated restoration withfurther input from the user, and/or without requiring additionalsoftware components. For example, and without limitation, a destinationlocation other than the original source location of the file(s) to berestored may be specified.

The present disclosure is also directed to a computer-based apparatusand a computing system configured to perform a method of datarestoration as described herein. Also disclosed is computer-readablemedia comprising a set of instructions of performing a method of datarestoration as described herein.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. The claims canencompass embodiments in hardware, software, or a combination thereof.Those skilled in the art will envision other modifications within thescope and spirit of the claims appended hereto.

What is claimed is:
 1. A method for retrieving a logical data unitstored within a backup set represented by at least one backup datablock, and an index file, comprising the steps of: identifying a backupdata block containing information indicative of the logical organizationof the backup set; identifying at least one logical data unit storedwithin the backup set; selecting at least one identified logical dataunit; and transferring the selected logical data unit to a recipient.